When working with samples, it is often required to keep these on ice at all times - even when working on them.

I wonder though... If I instead of using a ice-bucket with actual ice in it - instead substituted the ice with lots and lots of small stainless steel ball bearings cooled down to -20 to -22 degrees C - would they be able to keep cold for long enough in comparison with the real ice?

That would probably work, I would probably use them in conjunction with something like ice packs to do this if you want something re-usable. This would allow you to keep the bearings cold for longer, as the biggest problem would be conductance - steel conducts heat well, but ice doesn't so ice would keep colder for longer.

Note that in many instances you just want to keep the substance cold, not freeze it, which would be the risk you run when using frozen bearings.

In labtimes I read a tip to use cooled/frozen aquarium gravel (5-8 mm grain size) as substitute (just put the Styrofoam box with the gravels in a freezer to make it ready).

Reference: Anal. Biochem., 2015, 474, 38-39

One must presume that long and short arguments contribute to the same end. - Epicurus...except casandra's that did belong to the funniest, most interesting and imaginative (or over-imaginative?) ones, I suppose.

I just searched for styrofoam boxes in both Norway as well as on E-bay. I had no idea it was going to be so difficult to get something as simple as a styrofoam box. haha! In Norway it is impossible to find anywhere...

On e-bay I find lots of them - that does not ship internationally.

I guess I'll buy some enzymes from Bio-Rad and hold on the ice in the meanwhile... haha!